feat: add Envoy proxy support

[thebengeu]

Works as intended as far as I've tested with the all-in-one image and manually disabling Kong then enabling Envoy using the AMI.

• Envoy is disabled by default.
• The YAML config files are generated by https://github.com/supabase/infrastructure/blob/beng/envoy/worker/src/lib/config-utils/envoy.ts, better to review those there since there are comments.
• Referenced chore: Adding Envoy to the all-in-one image, not running be default #703 and WIP adding Envoy to the image #743 a bit, but mostly rewritten.
• Used /etc/envoy to be consistent with the official Envoy image, and there are many config files instead of just one, so https://github.com/supabase/supabase-admin-api/pull/174 won't work, Admin API changes in https://github.com/supabase/supabase-admin-api/pull/185.
• Keeping both kong and envoy in the services slice. I'm not sure what the issue was expected to be, when restarting using the services.slice, only running services are restarted, so restart doesn't say, restart kong if kong is stopped and envoy is running.